Royal Institution | 16th. January 1864.
My dear Helmholtz,
The reading of your excellent work on “Tonempfindungen”1 has excited in me the desire to have a syren2 such as you have there described. Sauerwald3 I think is the maker of it. I shall feel exceedingly obliged to you if you would have the kindness to order the instrument for me: I think the cost of it is about 60 thalers, but I should be willing to go to a little further expense if you thought it desirable.
I am also writing to Kirchhoff4 to ask him to be good enough to order a Spectroscope for me. Both instruments are for the Royal School of Mines;5 and the Government requires of us that we should have our accounts sent in before the end of March. If therefore Sauerwald cannot have the instrument constructed by the end of March he might send me his bill (quittert) and then I could send in the bill and allow him a little more time for the construction of the Syren.
We are all looking forward with pleasant anticipation to your course of lectures.6 If I can do anything to help you it will give me the greatest pleasure to do so.
Believe me | Yours most sincerely | John Tyndall
RI MS JT/1/T/481
LT Typescript Only
“Tonempfindungen”: see letter 2060, n. 8.
syren: a siren, or syren (as Tyndall often spelled it); an acoustical instrument (invented by Cagniard de la Tour in 1819) for producing musical tones and used in numbering the vibrations in any note (OED). The specific siren Tyndall referred to here was a double siren, composed of two of Dove’s polyphonic sirens with discs attached to a common axis. On each of the two discs of the sirens are four rows of holes, which can be either blown separately or together.
Sauerwald: Ferdinand Sauerwald, a German scientific instrument maker whose workshop was located in Berlin. He constructed apparatuses for Gustav Magnus, John Tyndall, Emil du Bois-Reymond, and Hermann Helmholtz, among others (D. Cahan: Helmholtz: A Life in Science (Chicago: University of Chicago Press, 2018), pp. 186, 264).
Kirchhoff: see letter 2070.
Royal School of Mines: see letter 1987, n. 4.
your course of lectures: see letter 2060, n. 7.
Please cite as “Tyndall2064,” in Ɛpsilon: The John Tyndall Collection accessed on